1. Field of the Invention
The present invention relates to a vapor-permeable shoe.
2. Discussion of the Background
It is known that a shoe, in order to be comfortable, must ensure correct exchange of heat and water vapor between the microclimate inside the shoe and the external microclimate. The exchanges of heat and vapor, however, must not compromise in any way the impermeability of the shoe to external humidity or water.
Currently commercially available shoes entrust the exchange of heat and water vapor substantially to the upper or to the sole. As regards the upper, shoes are commercially available which are perforated and/or provided with linings made of a vapor-permeable and waterproof material.
In some models, parts of the upper can be replaced with materials which are waterproof and at the same time vapor-permeable.
Another category of shoe instead entrusts transpiration to the sole, again by using layers of a waterproof and vapor-permeable material optionally associated with protective layers and fillers. These shoes, however, have not achieved an optimum exchange of heat and water vapor; accordingly, vapor-permeable shoes have been devised which are the subject of U.S. patent application 08/849,839, filed on Jun. 6, 1997, in which the shoe is constituted by the following elements: a vapor-permeable upper, associated with a vapor-permeable or perforated lining; a tread made of perforated elastomer; a mid-sole, which comprises at least one membrane made of vapor-permeable waterproof material associated with a lower protective layer made of a material which is resistant to hydrolysis, is water-repellent, vapor-permeable or perforated; and includes a vapor-permeable or perforated insole and a vapor-permeable or perforated filler layer arranged between said insole and said membrane.
The lower part of the upper, the tread and the mid-sole with the membrane are perimetrically sealed in the regions where they join.
Although this type of shoe solves many of the drawbacks observed in commercially available vapor-permeable shoes, it is not free from drawbacks, the main drawback being the fact that the vapor-permeable and waterproof membrane is not very strong from the mechanical point of view, is not protected in an optimum manner by the lower layer and can suffer damage due to interactions with blunt objects penetrating through the holes of the tread, which extend vertically with respect to the ground.
This type of shoe furthermore entails the drawback that the paths for the outflow of the air/water vapor mixture can clog at the sole, due to dirt wedging into the holes upon use.